Biomedical subjects
Publications and source records attributed to Shigeru Nishiyama.
Synthesis of the verbenachalcone derivatives 3-5 involving littorachalcone 2 from diaryl ether 7 enabled an SAR study of enhancement activity against the NGF-mediated neurite outgrowth from PC12D cells. Littorachalcone 2 and o-deoxyverbenachalcone 5 showed similar activity to that of verbenachalcone 1.
Halogenated cyclic isodityrosine-tripeptides were synthesized as analogues of a marine natural product, eurypamide B. Although the original eurypamides showed no inhibitory activity, the new analogues were found to inhibit lipid droplet accumulation in macrophages with a low micromolar IC50 value.
The novel naphthalene-type analogues 14 and 18 and the naphthoquinone-type analogues, 8, 9, 15, 16, 19, 21, 22, and 23-28 have been synthesized, and their in vitro Cdc25A phosphatase-inhibitory activity was examined. In assessment of the inhibitory activity, it was revealed that the naphthoquinone core is contributed to the activity, rather than the alkyl side chain.
A five-step and scalable synthesis of racemic cytoxazone, a novel cytokine modulator, was accomplished in a total yield of 51% from p-methoxycinnamyl alcohol without any protective groups. The keystep was the new one-pot azidohydroxylation procedure by the combined use of NaN3-H2O2-CH3CN. The epoxidation of an olefin by means of an in situ-formed iminohydroperoxide worked well, accompanied by the concomitant regioselective ring opening reaction of the resulting highly reactive epoxide with an azide ion.
A new and efficient route to (S)-azetidine-2-carboxylic acid (>99.9% ee) in five steps and total yield of 48% via malonic ester intermediates was established. As the key step, efficient four-membered ring formation (99%) was achieved from dimethyl (S)-(1'-methyl)benzylaminomalonate by treating with 1,2-dibromoethane (1.5 eq) and cesium carbonate (2 eq) in DMF. Krapcho dealkoxycarbonylation of dimethyl (1'S)-1-(1'-methyl)benzylazetidine-2,2-dicarboxylate, the product of this cyclization procedure, proceeded with preferential formation (2.7:1, 78% total yield) of the desired (2S,1'S)-monoester, with the help of a chiral auxiliary which was introduced on the nitrogen atom. The undesired (2R,1'S)-isomer could be converted to that with proper stereochemistry, by a deprotonation and subsequent re-protonation step. Finally, lipase-catalyzed preferential hydrolysis of the (2S,1'S)-monoester and subsequent deprotection provided enantiomerically pure (S)-azetidine-2-carboxylic acid in a 91% yield from the mixture of (2S,1'S)- and (2R,1'S)-isomers.
In addition to (+)-, (-)- and (+/-)-heliannuol E, growth-inhibitory activities of five synthetic chromans and four tetrahydrobenzo[b]oxepins were examined against oat and cress. All heliannuol E isomers exhibited similar biological activities against cress, whereas when tested against oat roots, the unnatural optical isomer (+) showed no inhibitory activity. Four brominated chromans and two tetrahydrobenzo[b]oxepin derivatives also showed apparent inhibition against both cress and oat.
Deprenyl and benzofenone-type congeners of alpha-mangostin 1 have been synthesized to understand their role for the inhibitory activity against sphingomyelinase (SMase). While removal of the prenyl group of the right side (11 and 12) caused loss of the selectivity between ASMase (acidic sphingomyelinase) and NSMase (neutral sphingomyelinase), the prenyl group of the left side appeared to increase the inhibitory activities (16 and 17).
The new diterpene glucoside 3,15-dihydroxy-ent-labd-7-en-17-oic acid 3-O-beta-D-glucoside (1) and its aglycone (2) have been isolated from Eupatorium glutinosum. The structures were determined by IR, one- and two-dimensional NMR, high-resolution mass spectrometry, chemical transformations, and comparison of spectroscopic data with closely related diterpenes. Crude extracts showed antimicrobial and cytotoxic activities, but compounds 1 and 2 showed only antimicrobial activity. These results support the vernacular medicinal use of the plant as an antimicrobial.
The absolute configuration was determined for the title compound, (-)-C(32)H(56)O(6)S(2)Si, (I), which was prepared in a synthetic study on the natural products bryostatins. Two independent molecules show similar conformations, except for the orientation of the methoxy groups.
The absolute configuration was determined for the title compound, (+)-C(18)H(24)O(3)S, (I), which was prepared in a synthetic study on the natural products, bryostatins.